Ink compositions

ABSTRACT

Disclosed is an ink composition which comprises (1) water; (2) a colorant; and (3) an additive selected from the group consisting of di-substituted guanidinium salts, wherein the substituents are alkyl groups, arylalkyl groups, or mixtures thereof.

BACKGROUND OF THE INVENTION

The present invention is directed to ink compositions. Morespecifically, the present invention is directed to compositions suitablefor use in ink jet printing processes. One embodiment of the presentinvention is directed to an ink composition which comprises (1) water;(2) a colorant; and (3) an additive selected from the group consistingof di-substituted guanidinium salts, wherein the substituents are alkylgroups, arylalkyl groups, or mixtures thereof.

Ink jet printing systems generally are of two types: continuous streamand drop-on-demand. In continuous stream ink jet systems, ink is emittedin a continuous stream under pressure through at least one orifice ornozzle. The stream is perturbed, causing it to break up into droplets ata fixed distance from the orifice. At the break-up point, the dropletsare charged in accordance with digital data signals and passed throughan electrostatic field which adjusts the trajectory of each droplet inorder to direct it to a gutter for recirculation or a specific locationon a recording medium. In drop-on-demand systems, a droplet is expelledfrom an orifice directly to a position on a recording medium inaccordance with digital data signals. A droplet is not formed orexpelled unless it is to be placed on the recording medium.

Since drop-on-demand systems require no ink recovery, charging, ordeflection, the system is much simpler than the continuous stream type.There are two types of drop-on-demand ink jet systems. One type ofdrop-on-demand system has as its major components an ink filled channelor passageway having a nozzle on one end and a piezoelectric transducernear the other end to produce pressure pulses. The relatively large sizeof the transducer prevents close spacing of the nozzles, and physicallimitations of the transducer result in low ink drop velocity. Low dropvelocity seriously diminishes tolerances for drop velocity variation anddirectionality, thus impacting the system's ability to produce highquality copies. Drop-on-demand systems which use piezoelectric devicesto expel the droplets also suffer the disadvantage of a slow printingspeed.

The other type of drop-on-demand system is known as thermal ink jet, orbubble jet, and produces high velocity droplets and allows very closespacing of nozzles. The major components of this type of drop-on-demandsystem are an ink filled channel having a nozzle on one end and a heatgenerating resistor near the nozzle. Printing signals representingdigital information originate an electric current pulse in a resistivelayer within each ink passageway near the orifice or nozzle, causing theink in the immediate vicinity to evaporate almost instantaneously andcreate a bubble. The ink at the orifice is forced out as a propelleddroplet as the bubble expands. When the hydrodynamic motion of the inkstops, the process is ready to start all over again. With theintroduction of a droplet ejection system based upon thermally generatedbubbles, commonly referred to as the "bubble jet" system, thedrop-on-demand ink jet printers provide simpler, lower cost devices thantheir continuous stream counterparts, and yet have substantially thesame high speed printing capability.

The operating sequence of the bubble jet system begins with a currentpulse through the resistive layer in the ink filled channel, theresistive layer being in close proximity to the orifice or nozzle forthat channel. Heat is transferred from the resistor to the ink. The inkbecomes superheated far above its normal boiling point, and for waterbased ink, finally reaches the critical temperature for bubble formationor nucleation of around 280° C. Once nucleated, the bubble or watervapor thermally isolates the ink from the heater and no further heat canbe applied to the ink. This bubble expands until all the heat stored inthe ink in excess of the normal boiling point diffuses away or is usedto convert liquid to vapor, which removes heat due to heat ofvaporization. The expansion of the bubble forces a droplet of ink out ofthe nozzle, and once the excess heat is removed, the bubble collapses onthe resistor. At this point, the resistor is no longer being heatedbecause the current pulse has passed and, concurrently with the bubblecollapse, the droplet is propelled at a high rate of speed in adirection towards a recording medium. The resistive layer encounters asevere cavitational force by the collapse of the bubble, which tends toerode it. Subsequently, the ink channel refills by capillary action.This entire bubble formation and collapse sequence occurs in about 10microseconds. The channel can be refired after 100 to 500 microsecondsminimum dwell time to enable the channel to be refilled and to enablethe dynamic refilling factors to become somewhat dampened. Thermal inkjet processes are well known and are described in, for example, U.S.Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899,U.S. Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530, the disclosures ofeach of which are totally incorporated herein by reference.

Acoustic ink jet printing processes are also known. As is known, anacoustic beam exerts a radiation pressure against objects upon which itimpinges. Thus, when an acoustic beam impinges on a free surface (i.e.,liquid/air interface) of a pool of liquid from beneath, the radiationpressure which it exerts against the surface of the pool may reach asufficiently high level to release individual droplets of liquid fromthe pool, despite the restraining force of surface tension. Focusing thebeam on or near the surface of the pool intensifies the radiationpressure it exerts for a given amount of input power. These principleshave been applied to prior ink jet and acoustic printing proposals. Forexample, K. A. Krause, "Focusing Ink Jet Head," IBM Technical DisclosureBulletin, Vol 16, No. 4, September 1973, pp. 1168-1170, the disclosureof which is totally incorporated herein by reference, describes an inkjet in which an acoustic beam emanating from a concave surface andconfined by a conical aperture was used to propel ink droplets outthrough a small ejection orifice. Acoustic ink printers typicallycomprise one or more acoustic radiators for illuminating the freesurface of a pool of liquid ink with respective acoustic beams. Each ofthese beams usually is brought to focus at or near the surface of thereservoir (i.e., the liquid/air interface). Furthermore, printingconventionally is performed by independently modulating the excitationof the acoustic radiators in accordance with the input data samples forthe image that is to be printed. This modulation enables the radiationpressure which each of the beams exerts against the free ink surface tomake brief, controlled excursions to a sufficiently high pressure levelfor overcoming the restraining force of surface tension. That, in turn,causes individual droplets of ink to be ejected from the free inksurface on demand at an adequate velocity to cause them to deposit in animage configuration on a nearby recording medium. The acoustic beam maybe intensity modulated or focused/defocused to control the ejectiontiming, or an external source may be used to extract droplets from theacoustically excited liquid on the surface of the pool on demand.Regardless of the timing mechanism employed, the size of the ejecteddroplets is determined by the waist diameter of the focused acousticbeam. Acoustic ink printing is attractive because it does not requirethe nozzles or the small ejection orifices which have caused many of thereliability and pixel placement accuracy problems that conventional dropon demand and continuous stream ink jet printers have suffered. The sizeof the ejection orifice is a critical design parameter of an ink jetbecause it determines the size of the droplets of ink that the jetejects. As a result, the size of the ejection orifice cannot beincreased, without sacrificing resolution. Acoustic printing hasincreased intrinsic reliability because there are no nozzles to clog. Aswill be appreciated, the elimination of the clogged nozzle failure modeis especially relevant to the reliability of large arrays of inkejectors, such as page width arrays comprising several thousand separateejectors. Furthermore, small ejection orifices are avoided, so acousticprinting can be performed with a greater variety of inks thanconventional ink jet printing, including inks having higher viscositiesand inks containing pigments and other particulate components. It hasbeen found that acoustic ink printers embodying printheads comprisingacoustically illuminated spherical focusing lenses can print preciselypositioned pixels (i.e., picture elements) at resolutions which aresufficient for high quality printing of relatively complex images. Ithas also has been discovered that the size of the individual pixelsprinted by such a printer can be varied over a significant range duringoperation, thereby accommodating, for example, the printing of variablyshaded images. Furthermore, the known droplet ejector technology can beadapted to a variety of printhead configurations, including (1) singleejector embodiments for raster scan printing, (2) matrix configuredejector arrays for matrix printing, and (3) several different types ofpagewidth ejector arrays, ranging from single row, sparse arrays forhybrid forms of parallel/serial printing to multiple row staggeredarrays with individual ejectors for each of the pixel positions oraddresses within a pagewidth image field (i.e., singleejector/pixel/line) for ordinary line printing. Inks suitable foracoustic ink jet printing typically are liquid at ambient temperatures(i.e., about 25° C.), but in other embodiments the ink is in a solidstate at ambient temperatures and provision is made for liquefying theink by heating or any other suitable method prior to introduction of theink into the printhead. Images of two or more colors can be generated byseveral methods, including by processes wherein a single printheadlaunches acoustic waves into pools of different colored inks. Furtherinformation regarding acoustic ink jet printing apparatus and processesis disclosed in, for example, U.S. Pat. No. 4,308,547, U.S. Pat. No.4,697,195, U.S. Pat. No. 5,028,937, U.S. Pat. No. 5,041,849, U.S. Pat.No. 4,751,529, U.S. Pat. No. 4,751,530, U.S. Pat. No. 4,751,534, U.S.Pat. No. 4,801,953, and U.S. Pat. No. 4,797,693, the disclosures of eachof which are totally incorporated herein by reference. The use offocused acoustic beams to eject droplets of controlled diameter andvelocity from a free-liquid surface is also described in J. Appl Phys.,vol. 65, no. 9 (May 1, 1989) and references therein, the disclosure ofwhich is totally incorporated herein by reference.

U.S. Pat. No. 5,626,654 (Breton et al.), the disclosure of which istotally incorporated herein by reference, discloses an ink compositionwhich comprises an aqueous liquid vehicle, a dye, and a vesicle-forminglipid, wherein vesicles of the lipid are present in the ink. Examples ofvesicle-forming lipids include glycerophospholipids, diacylglyceroles,α,ω-dipolar diacetyles, and the like.

U.S. Pat. No. 5,425,805 (Botros et al), the disclosure of which istotally incorporated herein by reference, discloses an ink jet inkcomposition comprising a liquid vehicle, a dye, and an N-hydroxyalkylbranched polyethyleneimine polymer or an N-hydroxyalkyldiphenylguanidine substituted at about 80% of the available nitrogens.The dye in this ink jet composition decreases the solubility of the inkand, therefore, can be used to formulate waterfast inks for ink jetprinters.

U.S. Pat. No. 5,403,955 (Farooq), the disclosure of which is totallyincorporated herein by reference, discloses mordants based upon apolyethyleneimine backbone and either pendant phosphonium orquaternized-nitrogen compounds. The mordants find use in stopping orcontrolling ink-bleeding into ink-jet receptors and photographic films.

U.S. Pat. No. 5,378,269 (Rossi et al.), the disclosure of which istotally incorporated herein by reference, discloses a recording liquidfor 5. ink-jet recording comprising coloring matter, which is animage-forming component, and a liquid medium for dissolving the coloringmatter therein. The liquid medium is ethanol and the coloring matter isa dye represented by the following general formula (A): ##STR1## or thefollowing general formula (B): ##STR2## as an image-forming component.

U.S. Pat. No. 5,334,435 (Rossi et al.), the disclosure of which istotally incorporated herein by reference, discloses a recording liquidfor ink-jet recording comprising coloring matter, which is animage-forming component, and a liquid medium for dissolving the coloringmatter therein. The liquid medium is ethanol and the coloring matter isa dye represented by the following general formula (A): ##STR3## or thefollowing general formula (B): ##STR4## as an image-forming component.

U.S. Pat. No. 4,840,674 (Schwarz), the disclosure of which is totallyincorporated herein by reference, discloses an improved ink compositioncomprising a major amount of water; an organic solvent selected from thegroup consisting of tetramethylene sulfone; 1,1,3,3-tetramethyl urea;3-methyl sulfolane; and 1,3-dimethyl-2-imidazolidone; which solvent haspermanently dissolved therein spirit soluble dyes such as black, yellow,cyan, magenta, brown, and mixtures thereof. At least one of the specificink compositions disclosed therein also contains diphenyl guanidiniumsulfate.

U.S. Pat. No. 5,019,166 (Schwarz), the disclosure of which is totallyincorporated herein by reference, discloses a thermal ink jet printingcomposition comprising a dye, a liquid medium, and a surfactant selectedfrom the group consisting of polyoxyalkylated ethers, anionic bitailfluorothio alkyls, alkyl aryl sulfonates, alkyl amine quaternary salts,and mixtures thereof. Also disclosed is a process for generating imageswhich comprises causing the ink compositions to be ejected from athermal ink jet printer in imagewise fashion onto a substrate.

With respect to issues of image permanence, until recently, littleattention has been paid to wet smear. Rather, waterfastness has been themost widely measured criterion of image permanence. While good wet smearcharacteristics may be found in waterfast inks, waterfastness of an inkdoes not guarantee that the ink will exhibit good wet smearcharacteristics. Wet smear is the mechanical displacement of the inkcolorant from a receiver sheet (such as paper, transparency, or thelike), subsequent to drying of the original image, when the dried imageis subjected to contact with a wet object, and primarily reflects howtightly the colorant is bound to the topmost areas of the receiversheet. Waterfastness is the degree to which water can resolvate andremove the ink colorant from the receiver sheet without mechanicalassistance. Binding of the colorant is common to and important for bothcharacteristics. Obtaining good wet smear characteristics, however, ismore difficult than obtaining good waterfastness, since wet smear has anadditional mechanical component thereto. A friable insoluble surface mayexhibit good waterfastness but poor wet smear; accordingly, solving theproblem of smear requires stabilization of the image surface, eitherwith or without also improving waterfastness. Obtaining good wet smearcharacteristics is particularly difficult with yellow inks, and alsoparticularly difficult with inks containing water soluble acid dyes orfood dyes.

While known compositions and processes are suitable for their intendedpurposes, a need remains for improved ink compositions suitable for inkjet printing processes. In addition, a need remains for ink compositionswith improved wet smear characteristics. Further, a need remains for inkcompositions containing water-soluble dye colorants that exhibitimproved wet smear characteristics. Additionally, a need remains for inkcompositions containing acid dye or food dye colorants that exhibitimproved wet smear characteristics. There is also a need for inkcompositions containing yellow acid dyes or food dyes that exhibitimproved wet smear characteristics. In addition, there is a need for inkcompositions containing Acid Yellow 23 dye that exhibit improved wetsmear characteristics. Further, there is a need for ink compositionsthat exhibit improved soaking waterfastness characteristics.

SUMMARY OF THE INVENTION

The present invention is directed to an ink composition which comprises(1) water; (2) a colorant; and (3) an additive selected from the groupconsisting of di-substituted guanidinium salts, wherein the substituentsare alkyl groups, arylalkyl groups, or mixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION

Inks of the present invention contain an aqueous liquid vehicle, acolorant, and a di-substituted guanidinium additive. The liquid vehiclecan consist solely of water, or it can comprise a mixture of water and awater soluble or water miscible organic component, such as ethyleneglycol, propylene glycol, diethylene glycols, glycerine, dipropyleneglycols, polyethylene glycols, polypropylene glycols, amides, ethers,urea, substituted ureas, ethers, carboxylic acids and their salts,esters, alcohols, organosulfides, organosulfoxides, sulfones (such assulfolane), alcohol derivatives, carbitol, butyl carbitol, cellusolve,tripropylene glycol monomethyl ether, ether derivatives, amino alcohols,ketones, N-methylpyrrolidinone, 2-pyrrolidinone, cyclohexylpyrrolidone,hydroxyethers, amides, sulfoxides, lactones, polyelectrolytes, methylsulfonylethanol, imidazole, betaine, and other water soluble or watermiscible materials, as well as mixtures thereof. When mixtures of waterand water soluble or miscible organic liquids are selected as the liquidvehicle, the water to organic ratio typically ranges from about 100:0 toabout 30:70, and preferably from about 97:3 to about 40:60. Thenon-water component of the liquid vehicle generally serves as ahumectant or cosolvent which has a boiling point higher than that ofwater (100° C.). In the ink compositions of the present invention, theliquid vehicle is typically present in an amount of from about 80 toabout 99.9 percent by weight of the ink, and preferably from about 90 toabout 99 percent by weight of the ink, although the amount can beoutside these ranges.

Ink compositions of the present invention also include a colorant. Dyesare suitable colorants for the inks of the present invention. Anysuitable dye or mixture of dyes compatible with the ink liquid vehiclecan be used, with water soluble anionic dyes and cationic dyes beingpreferred. Examples of suitable dyes include Food dyes such as FoodBlack No. 1, Food Black No. 2, Food Red No. 40, Food Blue No. 1, FoodYellow No. 7, and the like, FD & C dyes, Acid Black dyes (No. 1, 7, 9,24, 26, 48, 52, 58, 60, 61, 63, 92, 107, 109, 118, 119, 131, 140, 155,156, 172, 194, and the like), Acid Red dyes (No.1, 8, 32, 35, 37, 52,57, 92, 115, 119, 154, 249, 254, 256, and the like), Acid Blue dyes (No.1, 7, 9, 25, 40, 45, 62, 78, 80, 92, 102, 104, 113, 117, 127, 158, 175,183, 193, 209, and the like), Acid Yellow dyes (No. 3, 7, 17, 19, 23,25, 29, 38, 42, 49, 59, 61, 72, 73, 114, 128, 151, and the like), DirectBlack dyes (No. 4, 14, 17, 22, 27, 38, 51, 112, 117, 154, 168, and thelike), Direct Blue dyes (No. 1, 6, 8, 14, 15, 25, 71, 76, 78, 80, 86,90, 106, 108, 123, 163, 165, 199, 226, and the like), Direct Red dyes(No.1, 2, 16, 23, 24, 28, 39, 62, 72, 236, and the like), Direct Yellowdyes (No. 4, 11, 12, 27, 28, 33, 34, 39, 50, 58, 86, 100, 106, 107, 118,127, 132, 142, 157, and the like), Basic Yellow dyes (No. 17, 21, 51,and the like), Basic Red dyes (No. 1, 2, 5, 9, 29, and the like), BasicBlue dyes (No. 6, 7, 9, 11, 12, 16, 17, 24, 26, 41, 47, 66, and thelike); anthraquinone dyes, monoazo dyes, disazo dyes, phthalocyaninederivatives, including various phthalocyanine sulfonate salts,aza[18]annulenes, formazan copper complexes, triphenodioxazines,Bernacid Red 2BMN; Pontamine Brilliant Bond Blue A; Pontamine; Carodirect Turquoise FBL Supra Conc. (Direct Blue 199), available fromCarolina Color and Chemical; Special Fast Turquoise 8GL Liquid (DirectBlue 86), available from Mobay Chemical; Intrabond Liquid Turquoise GLL(Direct Blue 86), available from Crompton and Knowles; CibracronBrilliant Red 38-A (Reactive Red 4), available from Aldrich Chemical;Drimarene Brilliant Red X-2B (Reactive Red 56), available from Pylam,Inc.; Levafix Brilliant Red E-4B, available from Mobay Chemical; LevafixBrilliant Red E-6BA, available from Mobay Chemical; Procion Red H8B(Reactive Red 31), available from ICI America; Pylam Certified D&C Red#28 (Acid Red 92), available from Pylam; Direct Brilliant Pink B GroundCrude, available from Crompton & Knowles; Cartasol Yellow GTF Presscake,available from Sandoz, Inc.; Tartrazine Extra Conc. (FD&C Yellow #5,Acid Yellow 23), available from Sandoz; Carodirect Yellow RL (DirectYellow 86), available from Carolina Color and Chemical; Cartasol YellowGTF Liquid Special 110, available from Sandoz, Inc.; D&C Yellow #10(Acid Yellow 3), available from Tricon; Yellow Shade 16948, availablefrom Tricon, Basacid Black X34, available from BASF, Carta Black 2GT,available from Sandoz, Inc.; Neozapon Red 492 (BASF); Orasol Red G(Ciba-Geigy); Direct Brilliant Pink B (Crompton-Knolls); Aizen SpilonRed C-BH (Hodogaya Chemical Company); Kayanol Red 3BL (Nippon KayakuCompany); Levanol Brilliant Red 3BW (Mobay Chemical Company); LevadermLemon Yellow (Mobay Chemical Company); Spirit Fast Yellow 3G; AizenSpilon Yellow C-GNH (Hodogaya Chemical Company); Sirius Supra Yellow GD167; Cartasol Brilliant Yellow 4GF (Sandoz); Pergasol Yellow CGP(Ciba-Geigy); Orasol Black RL (Ciba-Geigy); Orasol Black RLP(Ciba-Geigy); Savinyl Black RLS (Sandoz); Dermacarbon 2GT (Sandoz);Pyrazol Black BG (ICI); Morfast Black Conc A (Morton-Thiokol); DiazolBlack RN Quad (ICI); Orasol Blue GN (Ciba-Geigy); Savinyl Blue GLS(Sandoz); Luxol Blue MBSN (Morton-Thiokol); Sevron Blue 5GMF (ICI);Basacid Blue 750 (BASF); Bernacid Red, available from Berncolors,Poughkeepsie, N.Y.; Pontamine Brilliant Bond Blue; Berncolor A.Y. 34;Telon Fast Yellow 4GL-1 75; BASF Basacid Black SE 0228; the Pro-Jet®series of dyes available from ICI, including Pro-Jet® Yellow I (DirectYellow 86), Pro-Jet® Magenta I (Acid Red 249), Pro-Jet® Cyan I (DirectBlue 199), Pro-Jet® Black I (Direct Black 168), Pro-Jet® Yellow 1-G(Direct Yellow 132), Aminyl Brilliant Red F-B, available from SumitomoChemical Company (Japan), the Duasyn® line of "salt-free" dyes availablefrom Clariant Corp., Charlotte, N.C., such as Duasyn® Direct BlackHEF-SF (Direct Black 168), Duasyn® Black RL-SF (Reactive Black 31),Duasyn® Direct Yellow 6G-SF VP216 (Direct Yellow 157), Duasyn® BrilliantYellow GL-SF VP220 (Reactive Yellow 37), Duasyn® Acid Yellow XX-SF LP413(Acid Yellow 23), Duasyn® Brilliant Red F3B-SF VP218 (Reactive Red 180),Duasyn® Rhodamine B-SF VP353 (Acid Red 52), Duasyn® Direct TurquoiseBlue FRL-SF VP368 (Direct Blue 199), Duasyn® Acid Blue AE-SF VP344 (AcidBlue 9), various Reactive dyes, including Reactive Black dyes, ReactiveBlue dyes, Reactive Red dyes, Reactive Yellow dyes, and the like, aswell as mixtures thereof. The dye is present in the ink composition inany effective amount, typically from about 0.5 to about 15 percent byweight, and preferably from about 1 to about 10 percent by weight,although the amount can be outside of these ranges.

Also suitable as a colorant are pigment particles. The pigment can be ofany desired color, such as black, cyan, magenta, yellow, red, blue,green, brown, or the like, as well as mixtures thereof. Examples ofsuitable pigments include various carbon blacks such as channel black,furnace black, lamp black, Raven® 5250, Raven® 5750, Raven® 3500 andother similar carbon black products available from Columbia Company,Regal® 330, Black Pearl® L, Black Pearl® 1300, and other similar carbonblack products available from Cabot Company, Degussa carbon blacks suchas Color Black® series, Special Black® series, Printtex® series andDerussol® carbon black dispersions available from Degussa Company,Hostafine® series such as Hostafine® Yellow GR (Pigment 13), Hostafine®Yellow (Pigment 83), Hostafine® Red FRLL (Pigment Red 9), Hostafine®Rubine F6B (Pigment 184), Hostafine® Blue2G (Pigment Blue 15:3),Hostafine® Black T (Pigment Black 7), and Hostafine® Black TS (PigmentBlack 7), available from Clariant Corp., Charlotte, N.C., NormandyMagenta RD-2400 (Paul Uhlich), Paliogen Violet 5100 (BASF), PaliogenViolet 5890 (BASF), Permanent Violet VT2645 (Paul Uhlich), HeliogenGreen L8730 (BASF), Argyle Green XP-111-S (Paul Uhlich), Brilliant GreenToner GR 0991 (Paul Uhlich), Heliogen Blue L6900, L7020 (BASF), HeliogenBlue D6840, D7080 (BASF), Sudan Blue OS (BASF), PV Fast Blue B2G01(Clariant Corp., Charlotte, N.C.), Irgalite Blue BCA (Ciba-Geigy),Paliogen Blue 6470 (BASF), Sudan Ill (Matheson, Coleman, Bell), Sudan II(Matheson, Coleman, Bell), Sudan IV (Matheson, Coleman, Bell), SudanOrange G (Aldrich), Sudan Orange 220 (BASF), Paliogen Orange 3040(BASF), Ortho Orange OR 2673 (Paul Uhlich), Paliogen Yellow 152, 1560(BASF), Lithol Fast Yellow 0991K (BASF), Paliotol Yellow 1840 (BASF),Novoperm Yellow FG1 (Clariant Corp., Charlotte, N.C.), Permanent YellowYE 0305 (Paul Uhlich), Lumogen Yellow D0790 (BASF), Suco-Gelb L1250(BASF), Suco-Yellow D1355 (BASF), Hostaperm Pink E (Clariant Corp.,Charlotte, N.C.), Fanal Pink D4830 (BASF), Cinquasia Magenta (DuPont),Lithol Scarlet D3700 (BASF), Toluidine Red (Aldrich), Scarlet forThermoplast NSD PS PA (Ugine Kuhlmann of Canada), E. D. Toluidine Red(Aldrich), Uthol Rubine Toner (Paul Uhlich), Lithol Scarlet 4440 (BASF),Bon Red C (Dominion Color Company), Royal Brilliant Red RD-8192 (PaulUhlich), Oracet Pink RF (Ciba-Geigy), Paliogen Red 3871 K (BASF),Paliogen Red 3340 (BASF), and Lithol Fast Scarlet L4300 (BASF). Otherpigments can also be selected. The pigment particles can be of anydesired size. Typical average particle diameters for pigment particlesin inks to be used in thermal ink jet printing processes, for example,are from about 0.001 to about 10 microns, preferably from about 0.01 toabout 3 microns, and more preferably less than about 1 micron, althoughthe average particle diameter can be outside these ranges. The pigmentparticles can be present in the ink in any desired amount. Typically thepigment particles are present in an amount of from about 1 to about 20percent by weight, preferably from about 1 to about 10 percent byweight, more preferably from about 2 to about 8 percent by weight, andeven more preferably from about 4 to about 7 percent by weight, althoughthe amount can be outside these ranges.

Mixtures of one or more dyes and/or one or more pigments can also beemployed for the colorant component of the inks of the presentinvention.

The ink compositions of the present invention also include adi-substituted guanidinium salt additive, wherein the substituents arealkyl groups, arylalkyl groups, or mixtures thereof. Thesedi-substituted guanidinium salts include those of the general formula##STR5## wherein R₁ and R₂ each, independently of the other, are alkylgroups, including saturated, unsaturated, and substituted alkyl groups,preferably linear, although some branching is acceptable, and preferablywith from about 12 to about 24 carbon atoms, more preferably with fromabout 14 to about 20 carbon atoms, and most preferably with from about16 to about 18 carbon atoms, although the number of carbon atoms can beoutside of these ranges, arylalkyl groups, preferably wherein the arylportion is bonded to the nitrogen atom, including those wherein thealkyl portion is saturated, unsaturated, or substituted, said alkylportion preferably being linear, although some branching is acceptable,said arylalkyl groups preferably with from about 14 to about 26 carbonatoms, more preferably with from about 16 to about 22 carbon atoms, andmost preferably with from about 18 to about 20 carbon atoms, althoughthe number of carbon atoms can be outside of these ranges, and whereinthe alkyl group or the alkyl portion of the arylalkyl group can besubstituted with fluorine atoms (such as a perfluoroalkyl group), saidperfluoro alkyl groups preferably having from about 8 to about 24 carbonatoms more preferably with from about 10 to about 20 carbon atoms, andmost preferably with from about 12 to about 1 8 carbon atom and saidaryl-perfluoroalkyl groups preferably having at least about 10 carbonatoms, to about 26 carbon atoms, more preferably with from about 12 toabout 22 carbon atoms, and most preferably with from about 14 to about20 carbon atom preferably with R₁ and R₂ having approximately equivalentchain lengths, most preferably with R₁ and R₂ each having carbon atomchains with the number of carbon atoms being within about 4 of thenumber of carbon atoms of the other, and wherein X is an anion, whereinn represents the charge on the anion, and typically is an integer of 1,2, or 3, although the value of n can be outside of this range. Anydesired or suitable anion can be employed; examples of suitable anionsinclude Cl⁻, Br, l⁻, HSO₄ ⁻, HSO₃ ⁻, SO₄ ²⁻, SO₃ ²⁻, CH₂ SO₃ ⁻, CH₃ SO₃⁻, CH₃ C₆ H₄ SO₃ ⁻, NO₃ ⁻, HCOO⁻, CH₃ COO⁻, HCO₃ ⁻, CO₃ ²⁻, H₂ PO₄ ⁻,HPO₄ ²⁻, PO₄ ³⁻, SCN⁻, BF₄ ⁻, ClO₄ ⁻, SSO₃ ⁻, and the like, as well asmixtures thereof. Particularly preferred R₁ and R₂ groups include oleyl,tallow, stearyl, and other hydrocarbons having about 16 or more carbonatoms. The di-substituted guanidinium salt is present in the ink in anydesired or effective amount, typically from about 0.2 to about 20percent by weight of the ink, preferably from about 0.5 to about 10percent by weight of the ink, and more preferably from about 1 to about5 percent by weight of the ink, although the amount can be outside ofthese ranges. Preferably, the di-substituted guanidinium salt is presentin a molar amount at least equal to that of the dye, to enable each dyemolecule to be associated with a di-substituted guanidinium molecule.Di-substituted guanidinium salts suitable for the present invention canbe made by any desired or suitable process. For example, cyanamide canbe treated with the appropriate amine, followed by acidification, asfollows: ##STR6## Suitable amine reactants are readily commerciallyavailable from, for example, Akzo Nobel, Inc., Chicago, Ill., or WitcoCorporation, Greenwich, Conn.

One particularly preferred member of the class of disubstitutedguanidinium salts is an ethoxylated octadecylamine-octadecylguanidinecomplex, and is a product of the reaction of cyanamide, carbon dioxide,ethylene oxide, and a long chain 1-alkylamine or 1-arylalkylamine. Thisreaction product is believed to be a mixture of materials of theformulae ##STR7## wherein R₁, R₂, R₃, and R₄ are each, independently ofthe other, alkyl groups, including saturated, unsaturated, andsubstituted alkyl groups, preferably linear, although some branching isacceptable, and preferably with from about 12 to about 24 carbon atoms,more preferably with from about 14 to about 20 carbon atoms, and mostpreferably with from about 16 to about 18 carbon atoms, although thenumber of carbon atoms can be outside of these ranges, arylalkyl groups,preferably wherein the aryl portion is bonded to the nitrogen atom,including those wherein the alkyl portion is saturated, unsaturated, orsubstituted, said alkyl portion preferably being linear, although somebranching is acceptable, said arylalkyl groups preferably with fromabout 14 to about 26 carbon atoms, more preferably with from about 16 toabout 22 carbon atoms, and most preferably with from about 18 to about20 carbon atoms, although the number of carbon atoms can be outside ofthese ranges, and wherein the alkyl group or the alkyl portion of thearylalkyl group can be substituted with fluorine atoms (such as aperfluoroalkyl group), said perfluoro alkyl groups preferably having atleast about 8 carbon atoms and said aryl-perfluoroalkyl groupspreferably having at least about 10 carbon atoms, preferably with R₁ andR₂ having approximately equivalent chain lengths, most preferably withR₁ and R₂ each having carbon atom chains with the number of carbon atomsbeing within about 4 of the number of carbon atoms of the other, and aand b are each integers of from 1 to about 6. Materials of this type arecommercially available as, for example, Aerosol C61, from AmericanCyanamid, New Jersey, and from Cytec Industries, Inc., West Paterson,N.J., wherein the material is the reaction product of cyanamide, carbondioxide, ethylene oxide, and a long chain 1-octadecylamine, and whereinR₁, R₂, R₃, and R₄ are each octadecyl groups.

In some instances, the disubstituted guanidinium salt is present incombination with a cosurfactant to improve solubility of the salt in theink. Examples of suitable cosurfactants include cationic monoquatemaryammonium salt surfactants, such as cationic coco methyl diethoxyquaternary ammonium salts, Ethoquad C/12, available from Akzo Nobel,Chicago, Ill., and the like. The cosurfactant is present in the ink inany desired or effective amount, typically from about 1 to about 5percent by weight of the ink, although the amount can be outside of thisrange. Generally, the cosurfactant is added to the ink subsequent toaddition of the disubstituted guanidinium salt; the disubstitutedguanidinium salt can tend to precipitate the colorant in the ink,especially when the colorant is a dye, and the cosurfactant is added inan amount sufficient to resolubilize the disubstituted guanidinium saltand the colorant, but not in excess of this amount, to avoid reducingwaterfastness and to avoid undesirable reduction of surface tension.

The disubstituted guanidinium salt additives are particularlyadvantageous in ink compositions containing relatively high amounts ofsolvent with respect to the water contained therein. In one preferredembodiment, the ink contains from about 5 to about 95 percent by weightwater, preferably from about 15 to about 80 percent by weight water, andmore preferably from about 25 to about 65 percent by weight water,although the amount can be outside of these ranges.

While not being limited to any particular theory, it is elieved that thedisubstituted guanidinium salts insolubilize anionic dye molecules onthe print substrate. In addition, it is believed that the guanidiniumgroups bind tightly to the paper surface, while the long hydrocarbontails extend outward from the surface, thereby providing slip andreducing wet smear. Adsorption to the paper is promoted not only by thecationic charge, but by multiple hydrogen bonds that are also availableto bind to the surface. In addition, the guanidinium salts can alsofunction as biocides, making the addition of a dedicated biocide to theink unnecessary in many instances.

Other optional additives to the inks include biocides such as Dowicil150, 200, and 75, benzoate salts, sorbate salts, and the like, presentin an amount of from about 0.0001 to about 4 percent by weight of theink, and preferably from about 0.01 to about 2.0 percent by weight ofthe ink, pH controlling agents such as acids or, bases, phosphate salts,carboxylates salts, sulfite salts, amine salts, and the like, present inan amount of from 0 to about 1 percent by weight of the ink andpreferably from about 0.01 to about 1 percent by weight of the ink, orthe like.

One example of an additive to the inks is a polymeric additiveconsisting of two polyalkylene oxide chains bound to a centralbisphenol-A-type moiety. This additive is of the formula ##STR8##wherein R¹ and R² are independently selected from the group consistingof hydrogen, alkyl groups with from 1 to about 8 carbon atoms, such asmethyl, ethyl, propyl, and the like, and alkoxy groups with from 1 toabout 8 carbon atoms, such as methoxy, ethoxy, butoxy, and the like, R³and R⁴ are independently selected from the group consisting of alkylgroups with from 1 to about 4 carbon atoms, and x and y are eachindependently a number of from about 100 to about 400, and preferablyfrom about 100 to about 200. Generally, the molecular weight of thepolyalkylene oxide polymer is from about 14,000 to about 22,000, andpreferably from about 15,000 to about 20,000, although the molecularweight can be outside this range. Materials of this formula arecommercially available; for example, Carbowax M20, a polyethyleneoxide/bisphenol-A polymer of the above formula with a molecular weightof about 18,000, available from Union Carbide Corporation, Danbury,Conn., is a suitable polymeric additive for the inks of the presentinvention. In addition, compounds of the above formula can be preparedby the methods disclosed in Polyethers, N. G. Gaylord, John Wiley &Sons, New York (1963) and "Laboratory Synthesis of Polyethylene GlycolDerivatives," J. M. Harris, J. Molecular Science--Rev. MacromoL Chem.Phys., C25(3), 325-373 (1985), the disclosures of each of which aretotally incorporated herein by reference. The polyalkylene oxideadditive is generally present in the ink in an amount of at least about1 part per million by weight of the ink. Typically, the polyalkyleneoxide additive is present in amounts of up to 1 percent by weight of theink, and preferably in amounts of up to 0.5 percent by weight of theink; larger amounts of the additive may increase the viscosity of theink beyond the desired level, but larger amounts can be used inapplications wherein increased ink viscosity is not a problem. Inkscontaining these additives are disclosed in U.S. Pat. No. 5,207,825, thedisclosure of which is totally incorporated herein by reference.

The ink compositions are generally of a viscosity suitable for use inink jet printing processes. At room temperature (i.e., about 25° C.),typically, the ink viscosity is no more than about 10 centipoise, andpreferably is from about 1 to about 5 centipoise, more preferably fromabout 1 to about 4 centipoise, although the viscosity can be outside ofthis range, especially for applications such as acoustic ink jetprinting.

Ink compositions of the present invention can be of any suitable ordesired pH. For some embodiments, such as thermal ink jet printingprocesses, typical pH values are from about 3 to about 11, preferablyfrom about 5 to about 10, and more preferably from about 7 to about 8,although the pH can be outside of these ranges.

Ink compositions suitable for ink jet printing can be prepared by anysuitable process. Typically, the inks are prepared by simple mixing ofthe ingredients. One process entails mixing all of the ink ingredientstogether and filtering the mixture to obtain an ink. Inks can beprepared by preparing a conventional ink composition according to anydesired process, such as by mixing the ingredients, heating if desired,and filtering, followed by adding any desired additional additives tothe mixture and mixing at room temperature with moderate shaking until ahomogeneous mixture is obtained, typically from about 5 to about 10minutes. Alternatively, the optional ink additives can be mixed with theother ink ingredients during the ink preparation process, which takesplace according to any desired procedure, such as by mixing all theingredients, heating if desired, and filtering. In a preferredembodiment, the ink ingredients are mixed in the following order: (1)water; (2) any salts present in the ink; (3) any cosolvents orhumectants present in the ink; (4) polyquaternary compound; (5) dye. Ifthe polyquaternary compound and the dye are added to water prior toaddition of salts and/or cosolvents and/or humectants, a precipitatedcomplex may form, which generally will tend to dissolve slowly tohomogeneity subsequent to addition of the other ink ingredients.

The present invention is also directed to a process which entailsincorporating an ink composition of the present invention into an inkjet printing apparatus and causing droplets of the ink composition to beejected in an imagewise pattern onto a substrate. In one embodiment, theprinting apparatus employs a thermal ink jet process wherein the ink inthe nozzles is selectively heated in an imagewise pattern, therebycausing droplets of the ink to be ejected in imagewise pattern. Inanother embodiment, the printer employs an acoustic ink jet process,wherein droplets of the ink are caused to be ejected in imagewisepattern by acoustic beams. Any suitable substrate can be employed,including plain papers such as Xerox® 4024 papers, Xerox® Image Seriespapers, Courtland 4024 DP paper, ruled notebook paper, bond paper,silica coated papers such as Sharp Company silica coated paper, JuJopaper, and the like, transparency materials, fabrics, textile products,plastics, polymeric films, inorganic substrates such as metals and wood,and the like. In a preferred embodiment, the process entails printingonto a porous or ink absorbent substrate, such as plain paper.

Specific embodiments of the invention will now be described in detail.These examples are intended to be illustrative, and the invention is notlimited to the materials, conditions, or process parameters set forth inthese embodiments. All parts and percentages are by weight unlessotherwise indicated.

CONTROL

A yellow ink composition was prepared by simple mixing of the followingingredients:

    ______________________________________                                                                       Amount                                         Ingredient       Supplier      (grams)                                        ______________________________________                                        PROJET YELLOW OAM (Acid                                                                        Zeneca Colors 2151.4                                         Yellow 23) dye*                                                               sulfolane**      Phillips Petroleum Co.                                                                      600                                            acetylethanolamine***                                                                          Scher Chemical                                                                              480                                            butyl carbitol   Van Waters & Rogers                                                                         480                                            urea             Arcadian Corp.                                                                              240                                            DOWICIL 150/200 biocide                                                                        Dow Chemical Co.                                                                            4                                              polyethylene oxide****                                                                         Polysciences  2                                              imidazole        American Biorganics                                                                         40                                             ethylene diamine tetraacetic                                                                   Dow Chemical Co.                                                                            2.6                                            acid                                                                          roll mill 30 minutes                                                          ______________________________________                                         *aqueous solution containing 7.5 wt. % dye solids and 92.5 wt. % water        **containing 95 wt. % sulfolane and 5 wt. % water                             ***aqueous solution containing 75 wt. % acetylethanolamine and 25 wt. %       water                                                                         ****bisphenolA derivative, molecular weight 18,500, of the formula            ##STR9##                                                                 

The resulting ink was filtered through a 1.2 micron Memtec filter at 20pounds per square inch. The resulting ink exhibited a viscosity of 3.66centipoise at 25° C., a pH of 8.37 at 23° C., a surface tension of 36.7dynes per centimeter, and a conductivity of 5.14 millimhos.

EXAMPLE I

Disubstituted guanidinium salts are prepared as follows. To 1 mole ofcyanamide is added two moles of a primary amine of the formula RNH₂,wherein the R group is oleyl, tallow, stearyl, or the like. Theingredients are admixed and heated; thereafter, hydrochloric acid isadde slowly to the reaction mixture to yield the disubstitutedguanidinium chloride salts.

The resulting dioleyl guanidinium chloride, ditallow guanidiniumchloride, and distearyl guanidinium chloride are each added to inkcompositions as described in the Control in an amount such that theresulting inks contai about 5 percent by weight of the disubstitutedguanidinium salt and about 5 percent by weight additional water. Forcomparison purposes, the ink of the Control is also diluted with waterin an amount such that the resulting ink contains about 10 percent byweight of the added water. The resulting inks are hand coated ontoXEROX® Image Series Smooth paper with a #7 Meyer rod. It is believedthat the waterdiluted ink of the Control will exhibit a waterfastness ofabout 50 percent (measured by determining the optical density of theimage before and after soaking in water for 5 minutes) and a wet smearof about 0.23 (measured by passing a weighted (100 grams pressure) watersaturated felt tip (similar to those found in marking pens) across theink image, which transfers some of the dye outside of the original imagearea and onto the adjacent virgin paper and measuring the opticaldensity of the dye transferred onto the virgin paper), whereas it isbelieved that the additivecontaining inks of this example will exhibit awaterfastness of at least about 70 percent and a wet smear of no morethan about 0.15.

EXAMPLE II

To two ink compositions prepared as described in the Control were added3 percent by weight of, respectively, ditallow amido ethylpolyoxyethylene methyl ammonium methosulfate (obtained from Lonza, Inc.,Fairllawn, N.J., as CARSOSOFT T90) and methylbis(oleylamido)2-hydroxyethyl ammonium methy sulfate (obtained fromWitco Chemical Co., Greenwich, Conn., as VARISOFT 222-LT). To enhancethe solubility of the diamido quaternary dialkyl ammonium salts in theink, to each ink was further added 3 percent by weight of acosurfactant, ETHOQUAD C/12 (obtained from Akzo Nobel, Chicago, Ill.)along with 4 percent by weight additional water. For comparisonpurposes, a third ink prepared as described in the Control was alsodiluted with water in an amount such that the resulting ink containeabout 10 percent by weight of the added water. The resulting inks werehand coated onto XEROX® Image Series Smooth paper with a #7 Meyer rodThe waterdiluted ink of the Control exhibited a waterfastness of about50 percent (measured by determining the optical density of the imagebefore and after soaking in water for 5 minutes) and a wet smear ofabout 0.23 (measured by passing a weighted (100 grams pressure) watersaturated felt tip (similar to those found in marking pens) across theink image, which transferred some of the dye outside of the originalimage area and onto the adjacent virgin paper, and measuring the opticaldensity of the dye transferred onto the virgin paper). In contrast, theink containing the ditallow amido ethyl polyoxyethylene methyl ammoniummethosulfate exhibited a waterfastness of about 74 percent and a wetsmear of 0.15, an the ink containing the methylbis(oleylamido)2-hydroxyethyl ammonium methyl sulfate exhibited awaterfastness of about 74 percent and a wet smear of 0. 15.

Other embodiments and modifications of the present invention may occurto those of ordinary skill in the art subsequent to a review of theinformation presented herein; these embodiments and modifications, aswel as equivalents thereof, are also included within the scope of thisinvention.

What is claimed is:
 1. An ink composition which comprises (1) water; (2)a colorant; and (3) an additive selected from the group consisting ofdi-substituted guanidinium salts, wherein the substituents are alkylgroups, arylalkyl groups, or mixtures thereof.
 2. An ink compositionaccording to claim 1 wherein the colorant is an anionic dye.
 3. An inkcomposition according to claim 1 wherein the colorant is an Acid dye ora Food dye.
 4. An ink composition according to claim 1 wherein thecolorant is a yellow dye.
 5. An ink composition according to claim 1wherein the colorant is Acid Yellow 23 dye.
 6. An ink compositionaccording to claim 1 wherein the di-substituted guanidinium salt is ofthe formula ##STR10## wherein R₁ and R₂ each, independently of theother, are alkyl groups, perfluoroalkyl groups, arylalkyl groups,arylperfluoroalkyl groups, or mixtures thereof, X is an anion, and n isan integer representing the charge on the anion.
 7. An ink compositionaccording to claim 6 wherein the alkyl groups have from about 12 toabout 24 carbon atoms, the arylalkyl groups have from about 14 to about26 carbon atoms, the perfluoroalkyl groups have from about 8 to about 24carbon atoms, and the arylperfluoroalkyl groups have from about 10 toabout 26 carbon atoms.
 8. An ink composition according to claim 6wherein the alkyl groups have from about 14 to about 20 carbon atoms,the arylalkyl groups have from about 16 to about 22 carbon atoms, theperfluoroalkyl groups have from about 10 to about 20 carbon atoms, andthe aryiperfluoroalkyl groups have from about 12 to about 22 carbonatoms.
 9. An ink composition according to claim 6 wherein the alkylgroups have from about 16 to about 18 carbon atoms, the arylalkyl groupshave from about 18 to about 20 carbon atoms, the perfluoroalkyl groupshave from about 12 to about 18 carbon atoms, and the arylperfluoroalkylgroups have from about 14 to about 20 carbon atoms.
 10. An inkcomposition according to claim 1 wherein the di-substituted guanidiniumsalt is an ethoxylated octadecylamine-octadecylguanidine complex, saidcomplex being a product of the reaction of cyanamide, carbon dioxide,ethylene oxide, and a long chain 1-alkylamine or 1-arylalkylamine. 11.An ink composition according to claim 10 wherein the ethoxylatedoctadecylamine-octadecylguanidine complex salt is of the formula##STR11## wherein R₁, R₂, R₃, and R₄ are each, independently of theother, alkyl groups, perfluoroalkyl groups, arylalkyl groups,arylperfluoroalkyl groups, or mixtures thereof wherein a and b are eachintegers of from 1 to about
 6. 12. An ink composition according to claim1 wherein the di-substituted guanidinium salt is present in an amount offrom about 0.2 to about 20 percent by weight.
 13. An ink compositionaccording to claim 1 further containing a cosurfactant.
 14. An inkcomposition according to claim 13 wherein the cosurfactant is a cationicmonoquaternary ammonium salt.
 15. An ink composition according to claim1 wherein the di-substituted guanidinium salt is present in the ink in amolar amount at least equal to that of the dye molecules.
 16. An inkcomposition prepared by admixing (1) water; (2) a colorant; and (3) anadditive selected from the group consisting of di-substitutedguanidinium salts, wherein the substituents are alkyl groups, arylalkylgroups, or mixtures thereof.
 17. A process which comprises (i)incorporating into an ink jet printing apparatus an ink compositionaccording to claim 1; and (ii) causing droplets of the ink compositionto be ejected in an imagewise pattern onto a substrate.
 18. A processaccording to claim 17 wherein the printing apparatus employs a thermalink jet process wherein the ink in the nozzles is selectively heated inan imagewise pattern, thereby causing droplets of the ink to be ejectedin imagewise pattern.
 19. A process according to claim 17 wherein theprinting apparatus employs an acoustic ink jet process wherein dropletsof the ink are caused to be ejected in imagewise pattern by acousticbeams.
 20. A process for reducing wet smear in images subsequent toprinting of the images on a substrate which comprises (a) providing anink composition according to claim 1; (b) incorporating the ink into anink jet printer; and (c) causing droplets of the ink to be ejected in animagewise pattern.